Revert "document.documentElement.scrollTop/Left is zero"

This reverts https://src.chromium.org/viewvc/blink?revision=158719&view=revision

This patch was breaking telemetry unittests (scrollAction: e.g. http://build.chromium.org/p/chromium.webkit/builders/Vista%20Tests/builds/33554/steps/telemetry_unittests/logs/stdio) and blocking the blink roll in chromium.

TBR=jchaffraix@chromium.org
BUG=

Review URL: https://codereview.chromium.org/25767003

git-svn-id: svn://svn.chromium.org/blink/trunk@158749 bbb929c8-8fbe-4397-9dbb-9b2b20218538